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    From Cardiovascular System

    Small Cardiac Vein
    Drains right atrium and ventricle.
    Basilic Veins
    Superficial veins of the medial upper limb.
    Superior Vena Cava
    Returns deoxygenated blood from upper body.
    External Carotid Artery
    Supplies blood to the face and scalp.
    Axillary Veins
    Drain the upper limbs and join with subclavian veins.
    Marginal Branch
    Supplies right ventricle along the margin.
    Parietal Layer
    Lines the internal surface of the fibrous pericardium.
    Internal Iliac Arteries
    Supply blood to pelvic organs.
    Trabeculae Carneae
    Irregular muscular columns on the walls of the ventricles.
    Mitral Valve
    Valve between the left atrium and left ventricle.
    Middle Cardiac Vein
    Drains the posterior heart.
    Fossa Ovalis
    Remnant of the fetal foramen ovale.
    Anterior Cardiac Veins
    Drain directly into the right atrium.
    Dorsal Venous Arch
    Superficial venous network on the dorsum of the foot.
    Aortic Arch
    Curved portion of the aorta giving rise to major arteries.
    Coronary Sinus
    Collects blood from coronary veins.
    Posterior Tibial Arteries
    Supply posterior compartment of the leg.
    Right Ventricle
    Pumps blood to the lungs via pulmonary artery.
    Left Subclavian Artery
    Supplies the left upper limb.
    Left Atrium
    Receives oxygenated blood from the lungs.
    Anterior Interventricular Branch
    Supplies anterior interventricular septum (LAD).
    Pericardium
    Double-walled sac containing the heart and the roots of the great vessels.
    Common Carotid Arteries
    Major arteries supplying blood to the head and neck.
    Common Iliac Arteries
    Branch from abdominal aorta to supply the lower limbs.
    Popliteal Veins
    Drain blood from the knee region.

    Auricles

    Reviewed by our medical team

    Small muscular pouches of each atrium.

    1. Overview

    The auricles, also known as the atrial appendages, are small, muscular pouches that are located on the anterior (front) surface of the atria of the heart. There are two auricles in the heart, one attached to the right atrium and the other to the left atrium. They are considered an extension of the atria and serve specific physiological roles in the circulation of blood within the heart. Though they are not essential for heart function, the auricles assist with the efficiency of blood flow and play a role in regulating heart pressure and volume. Their structure and function make them important in the context of certain cardiovascular diseases, especially conditions that affect atrial pressure and rhythm.

    2. Location

    The auricles are located on the outer walls of the right and left atria of the heart. Each auricle is positioned in such a way that it extends slightly above the main body of the atrium, protruding towards the outside of the heart. The right auricle is attached to the right atrium and lies near the superior vena cava and the right atrioventricular (AV) valve. The left auricle is similarly attached to the left atrium and is situated near the pulmonary veins. Both auricles are positioned in front of the atrial appendages and help to increase the volume of the atria for better blood reception.

    3. Structure

    The auricles are distinct anatomical features of the atria that have specific structural characteristics:

    • Shape: The auricles are typically conical or pouch-shaped structures, which help expand the atrial volume. The left auricle is slightly more prominent and can sometimes resemble a "dog's ear" in shape, due to its small muscular appendage. The right auricle is also pouch-like but less pronounced.

    • Muscular walls: The walls of the auricles are made up of smooth muscle, which is different from the other chambers of the heart. These muscular walls help contract during atrial systole (the phase of the heart cycle when the atria contract to push blood into the ventricles), contributing to the efficient movement of blood into the ventricles.

    • Trabeculations: The inner surfaces of the auricles are lined with trabeculae, which are small, muscular ridges that help increase the contractile surface area. These trabeculae are more prominent in the right auricle and help regulate atrial contraction.

    • Connection to the atria: The auricles are directly connected to the atrial chambers through the opening that leads to the atrioventricular valves (right and left). The blood flow from the auricles to the atria allows blood to move efficiently between the heart's upper chambers.

    4. Function

    Although not essential to the basic function of the heart, the auricles contribute to several important processes related to cardiac function:

    • Increased atrial volume: The auricles act as reservoirs that increase the volume of the atria, providing extra space for blood to accumulate before being pumped into the ventricles. This function is particularly important during situations where the heart rate is elevated, such as during exercise, as it allows the atria to accommodate more blood.

    • Assisting in blood flow: The auricles help augment the flow of blood into the ventricles during atrial systole. When the atria contract, the auricles help propel any remaining blood into the ventricles. This ensures the ventricles are adequately filled with blood during each heart cycle, improving cardiac efficiency.

    • Regulation of atrial pressure: The auricles help regulate the pressure in the atria by providing extra space to handle blood volume fluctuations. When atrial pressure rises, the auricles help accommodate the increased volume, helping to maintain steady pressure levels in the heart.

    • Blood storage in diastole: The auricles act as a secondary reservoir for blood during diastole (the relaxation phase of the heart cycle). This allows for optimal ventricular filling during systole and ensures that there is enough blood supply to the heart during moments of increased demand.

    5. Physiological Role(s)

    The physiological roles of the auricles are important for the optimal functioning of the heart and for maintaining the overall efficiency of the cardiovascular system:

    • Support of cardiac function: By providing additional space for blood during the cardiac cycle, the auricles ensure that the ventricles receive adequate filling, which is essential for maintaining an effective stroke volume (the amount of blood pumped with each heartbeat).

    • Pressure regulation: The auricles help manage the pressure in the atria, particularly during times of increased cardiac output, such as during physical exertion. By serving as reservoirs and buffering spaces, they prevent excessive pressure buildup in the atria that could lead to heart dysfunction.

    • Facilitating atrial contraction: The muscular walls of the auricles allow for contraction that aids in the propulsion of blood into the ventricles. This contributes to the efficiency of the atrial systole, helping to optimize ventricular filling during the heart cycle.

    • Supporting atrial fibrillation management: The auricles play a role in the heart’s response to atrial fibrillation (AFib), which is a condition where the atria beat irregularly. The left auricle, in particular, can become a site for thrombus (clot) formation during AFib, which can lead to complications such as stroke. Managing auricular health is key to preventing these risks.

    6. Clinical Significance

    The auricles are clinically significant, particularly in conditions that involve abnormal atrial function, arrhythmias, and thrombus formation. Some key clinical conditions associated with the auricles include:

    • Atrial fibrillation (AFib): AFib is a common arrhythmia characterized by irregular electrical activity in the atria. This condition often involves dysfunction in the auricles, particularly the left auricle, which can lead to blood pooling and the formation of blood clots. These clots can travel to the brain and cause a stroke. Anticoagulation therapy is often used to reduce the risk of stroke in AFib patients.

    • Left atrial thrombus formation: The left auricle is the most common site for thrombus formation in patients with AFib or other forms of atrial dysfunction. The stasis of blood in the auricle, combined with irregular atrial contractions, creates an environment where blood clots can form. These clots can embolize (travel to other areas) and cause serious complications like stroke, heart attack, or organ damage.

    • Auricular enlargement: In some heart conditions, such as valvular heart disease, hypertension, or heart failure, the auricles may enlarge due to increased pressure and volume load. This enlargement can worsen the function of the auricles, leading to further complications with blood flow and increasing the risk of clot formation.

    • Atrial septal defect (ASD): ASD is a congenital heart defect where there is an opening between the left and right atria, often affecting the auricles. This can lead to blood mixing between the chambers, increased workload on the right side of the heart, and eventually, pulmonary hypertension or heart failure. Surgical correction may be needed in severe cases.

    • Cardiac surgery complications: During certain cardiac surgeries, such as valve replacement or repair, the auricles may be inadvertently affected. Damage to the auricles during these procedures can impair atrial function, leading to issues with blood flow and potential arrhythmias in the post-operative period.

    • Patent foramen ovale (PFO): A PFO is a small hole in the septum between the left and right atria that may persist from fetal development. It is a relatively common condition that can lead to stroke or paradoxical embolism (where a clot from the venous side crosses into the arterial system). While the auricles themselves are not always the source, their dysfunction can contribute to the condition.

    The auricles are integral components of the heart's atrial anatomy, contributing to the regulation of atrial pressure, blood flow, and cardiac efficiency. Although they are not essential for basic heart function, the auricles play a role in maintaining proper cardiac performance. Dysfunction or abnormalities in the auricles can lead to serious cardiovascular conditions, including arrhythmias, clot formation, and heart failure. Proper diagnosis and management of auricular-related conditions are essential for preventing complications and ensuring optimal heart health.

    Did you know? The heart has its own electrical system and can beat independently of the body when separated.